The big opening on the carbed intake could have the narrow 2-barrel TBI positioned forward, rearward, or on-center.
When it was me, I think I bought the on-center adapter--but Summit's web site has deleted my purchase history for orders that long ago so I'm not absolutely sure.
Whatever I bought for my 350/ZZ4 intake manifold, (not a Vortec design) it positioned the TBI unit just a little bit higher and a touch farther-forward than the OEM manifold. I had to re-adjust my TV cable, but the throttle cable and cruise cable connected just fine.